Patent application title: Smoking Article Filter

Abstract:

A filter for a smoking article comprising first and second sections, the
first section being at the mouth end of the filter and comprising a
cylindrical element circumscribed by a wrapper and having a hollow
portion extending therethrough, and the second section being
longitudinally aligned with and adjacent to the first section and
comprising a filtration material. The second section comprises a
particulate material in a circumferential region and extending to the end
of the second section immediately adjacent the first section. Also
provided is a smoking article incorporating a filter according to the
invention.

Claims:

1. A filter for a smoking article comprising a first and a second section,
the first section being at a mouth end of the filter and comprising a
cylindrical element having a hollow portion extending therethrough and
being circumscribed by a wrapper, and the second section being
longitudinally aligned with and adjacent to the first section and
comprising a filtration material, wherein the second section comprises a
particulate material in a circumferential region thereof, the particulate
material extending to an end of the second section immediately adjacent
the first section.

2. The filter according to claim 1, wherein the particulate material
extends over a full longitudinal length of the second section.

3. The filter according to claim 1, wherein two or more portions of the
circumferential region of the second section comprise particulate
material.

4. The filter according to claim 3, wherein the two or more portions are
spaced circumferentially from one another.

5. The filter according to claim 4, wherein the two or more portions are
arranged symmetrically around the second section.

6. The filter according to claim 1, wherein a wrapper surrounds the second
section and the particulate material is adhered to a surface of the
wrapper.

7. The filter according to claim 6, wherein the particulate material is
adhered to an inner surface of the wrapper surrounding the second
section.

8. The filter according to claim 1, wherein the particulate material is an
adsorbent.

9. The filter according to claim 8, wherein the particulate material is
activated carbon.

10. The filter according to claim 1, wherein the second section further
comprises a particulate material interspersed in the filtration material.

11. The filter according to claim 1, wherein the cylindrical element has a
wall defined by the outer surface of the element and the hollow portion
extending therethrough, the wall being of a thickness to at least partly
occlude the particulate material in a circumferential region of the
second section at the point of abutment of the first and second sections.

12. The filter according to claim 1, wherein the wrapper circumscribing
the first section is a plugwrap.

13. The filter according to claim 12, wherein the plugwrap has a base
weight of less than 50 g/m.sup.2.

14. The filter according to claim 1, wherein the cylindrical element of
the first section comprises cellulose acetate.

15. The filter according to claim 1, further comprising at least one
additional filter section at the tobacco rod end of the filter.

16. The filter according to claim 1 wherein two or more portions of the
circumferential region of the second section comprise particulate
material, and the two or more portions are spaced circumferentially from
one another, wherein a wrapper surrounds the second section and the
particulate material is adhered to a surface of the wrapper, and the
particulate material is adhered to an inner surface of the wrapper
surrounding the second section.

17. The filter according to claim 1 configured as a component within a
smoking article.

Description:

[0001]The present invention relates to a filter for a smoking article and
smoking articles incorporating a filter element.

[0002]Smoking articles, and filters therefore, can vary significantly from
one market to another as a result of many different factors including
consumer preference and tradition. In certain markets there is a
preference for a filter having a recess at the mouth end, which may be
used to lengthen the filter as a whole. The recess is achieved by
overwrapping the plug of filtration material with a plugwrap that extends
beyond the end of the plug of filtration material at the mouth end of the
filter. In order to minimise the susceptibility of the overhanging
portion of the plugwrap to damage and deformation, for example as may
result from the packaging process or during handling and smoking by a
consumer, a plugwrap which is thicker than a conventional cigarette
plugwrap is used. Such a plugwrap has up to four times the base weight of
a conventional plugwrap and thus is significantly more resistant to
deformation and adds a high level of rigidity at the mouth end of the
filter. However, the need for such a thick plugwrap means that
conventional (more economical) plugwraps cannot be used on filters having
a recessed end and also add significant problems to the process of
ventilating the filter, and in particular to the process of online laser
perforation of the filter, thus not allowing high levels of ventilation
to be attained.

[0004]The present invention provides a filter for a smoking article
comprising a first and a second section, the first section being at a
mouth end of the filter and comprising a cylindrical element having a
hollow portion extending therethrough and being circumscribed by a
wrapper, and the second section being longitudinally aligned with and
adjacent to the first section and comprising a filtration material. The
second section comprises a particulate material in a circumferential
region thereof, the particulate material extending to the end of the
second section immediately adjacent the first section.

[0005]The use of particulate materials, such as carbon or activated
carbon, in tobacco smoke filter elements to reduce vapour phase
constituents of smoke has been known for some while. A known way of
including carbon or other additives in filters is to adhere particles of
the additive to a wrapper surrounding the filter element. GB 2,260,477
and GB 2,261,152 describe various configurations of additive adhesion. In
some circumstances, particulate carbon, when provided in a mouth end
filter section, may be liable to fall out of the end of the filter. This
is highly undesirable as it is possible that particulate carbon may
become loose and enter the mouth of the consumer. The provision of a
first filter section at the mouth end of the filter having a hollow
portion extending therethrough helps to prevent the fall out of the
particulate material whilst maintaining the appearance of a recessed
filter.

[0006]The particulate material may extend over the full longitudinal
length of the second section. The particulate material may also extend
over the full width of the wrapper. In this instance the particulate
material may cover the entire surface of the wrapper, although a seam may
be left uncovered to allow adhesive to be applied and the wrapper to be
sealed about the filtration material. Alternatively, the particulate
material may extend over only a portion of the longitudinal length of the
wrapper. Similarly, the particulate material may extend over only a
portion of the width of the wrapper.

[0007]The particulate material may extend over two or more portions of the
second section. The two or more portions are preferably spaced
circumferentially from one another.

[0008]Alternatively, the two or more portions may comprise three, four,
five, six, seven or eight portions.

[0009]In some embodiments, the filtration material of the second section
may further comprise a particulate material interspersed in the
filtration material.

[0010]The particulate material of the filtration material may be the same
as the particulate material provided at the circumferential region of the
second section of the plugwrap. Alternatively, the particulate material
of the filtration material may be different from the particulate material
provided at the circumferential region of the second section of the
plugwrap.

[0011]In some embodiments, the wrapper may further comprise ventilation
means. For example, the ventilation means may comprise one or more
ventilation holes provided in gaps between the two or more portions.

[0012]The cylindrical element will generally have a thickness (in the
radial direction) sufficient to occlude at least part of the particulate
material. In other words, the cylindrical element acts as a physical
barrier located at the mouth end of the particulate material to prevent
the particular material from escaping from the second section of the
filter. The thickness of the cylindrical element may be from 1-4 mm, and
is preferably in the range 1-3 mm.

[0013]Suitably the cylindrical element is circumscribed by a wrapper,
which is preferably a plugwrap. This plugwrap may have a base weight of
less than 50 g/m2, less than 45 g/m2, less than 40 g/m2,
less than 35 g/m2, less than 30 g/m2. This plugwrap may have a
base weight equivalent to a conventional plugwrap (wrapper), namely
approximately 23 to approximately 27 g/m2.

[0014]A second aspect of the present invention provides a smoking article
comprising a filter according to the invention.

[0016]Advantageously the particulate material is selected from a group of
relatively high surface area materials capable of adsorbing smoke
constituents without a high degree of specificity. Suitable general
adsorbents can be selected from the group consisting of carbon, activated
carbon, activated charcoal, activated coconut carbon, activated
coal-based carbon or charcoal, zeolite, silica gel, meerschaum, aluminium
oxide (activated or not), carbonaceous resin or combinations thereof.

[0017]An example of a suitable coal-based charcoal is one made from
semi-anthracite coal with a density about 50% greater than coconut-based
charcoal (available from Calgon Carbon, Pittsburgh, Pa., WA).

[0018]An example of a suitable carbonaceous resin is one derived from the
pyrolysis of sulphonated styrene-divinyl benzene, such as Ambersorb 572
or Ambersorb 563 (available from Rohm and Haas). To enhance the
efficiency of the general adsorbent metal oxides or other metal based
complexes may optionally be included in or impregnated on the general
adsorbent section.

[0019]In one embodiment, preferably the particulate material used herein
is carbon, for instance activated carbon, or charcoal or other absorbent
material. In one embodiment, preferably the activated carbon is activated
coconut carbon.

[0020]Any particulate material used may be a single substance or a
mixture, and/or may be in admixture with other material.

[0021]In one embodiment preferably the particulate material is disposed in
two separate regions spaced circumferentially from one another.
Alternatively, the particulate material may be disposed in 3, 4, 5, 6, 7
or 8 separate regions each spaced circumferentially from one another.
Further, a greater number of regions may be used if required.

[0022]Each separate region or portion of particulate material may be
comprised of particulate material which is the same as or different from
the other separate regions. In one embodiment preferably the particulate
material in the separate regions is the same.

[0023]In one embodiment, suitably the particulate material may be applied
to two or more portions of the longitudinal inner face of the wrapper.

[0024]In one embodiment the particulate material is disposed around the
inner circumference of the wrapper such that the wrapper has an
overlapping longitudinal edge which is free of said particulate material
and which provides a lapped and stuck seam holding the wrapper around the
core.

[0025]The particulate material may extend continuously over the full
longitudinal length of said wrapper. By continuously it is meant that the
particulate material is applied such that the loading at any one point on
the longitudinal length of the wrapper is the same (or substantially the
same) as the loading at any other point on the same longitudinal length
of the wrapper. By continuously it is meant that at no point along the
longitudinal length of the wrapper is there a portion of the wrapper
without particulate material if the particulate material is present at
another point along the same longitudinal length of the wrapper.
Preferably, the particulate material is applied longitudinally to the
wrapper (e.g. plugwrap) in a continuous manner. Preferably along the
longitudinal axis of the wrapper the particulate material is present as a
continuous stream (i.e. without breaks or spaces). In other words, the
particulate material extends in a continuous manner along the
longitudinal axis of the wrapper.

[0026]The particulate material may extend continuously over the full width
of said wrapper.

[0027]In some embodiments the particulate material may be present as
patches.

[0028]The wrapper of the filter element is preferably a paper wrapper.
Preferably the wrapper is a conventional plugwrap.

[0029]In one embodiment the wrapper may be a conventional plugwrap which
covers 360° of the core, in which case the plugwrap has a lapped
and stuck seam holding the wrapper around the core.

[0030]In one embodiment, preferably the filter element according to the
present invention has a filtration material comprising particulate
material interspersed with the filtration material and has a plugwrap
which covers 360° of the filtration material.

[0031]In another embodiment the wrapper (in particular plugwrap)
preferably does not extend 360° around the filtration material. In
other words, in one embodiment preferably the wrapper is a split wrapper.
A split wrapper is one which extends circumferentially about the
filtration material, but extends less than 360° around the
circumference of the filtration material. In such an embodiment, there is
not lapped and stuck seam holding the wrapper around the filtration
material. Instead, the split wrapper may be held in place by other known
means, such as by bonding the wrapper directly to the filtration material
for instance.

[0032]The wrapper for use in the filter element may be porous or
non-porous.

[0033]The wrapper for use in the filter element may be ventilated or
unventilated.

[0036]In one embodiment, the filtration material of the second section is
a Dalmatian-type filter material.

[0037]The particulate material may be interspersed throughout the
filtration material. Alternatively, the particulate material may be
interspersed in some parts (but not all) of the filtration material. The
parts may be evenly or unevenly distributed.

[0038]The particulate material adhered to the wrapper may be
homogenous--in the sense that it is made up of substantially the same
component (for some embodiments, preferably all of the same).
Alternatively, the particulate material adhered to the wrapper may be
heterogeneous--in the sense that it is made up of two or more different
components. The particulate material adhered to the wrapper may be in
contact with the filtration material. Preferably, some or all of the
particulate material adhered to the wrapper is in contact with the
filtration material. For some embodiments, preferably substantially all
of the particulate material adhered to the wrapper is in contact with the
filtration material.

[0039]The filter is preferably interattached with a smokable filler (e.g.
tobacco) rod by way of a tipping wrapper. Advantageously the tipping
wrapper is a paper.

[0040]In one embodiment the filter may comprise additional filter
section(s). The additional filter section(s) will be at the tobacco rod
end of the filter. Suitably, one, two, three or more additional filter
sections may be provided in the filter. The additional filter section(s)
may be any type of filter section known to those skilled in the art.
Suitably the filter sections are arranged longitudinally of one another
with the end of each filter element abutting the next.

[0041]Suitably the wrapper surrounding the second section of the filter is
preferably pre-coated with the particulate material.

[0042]The particulate material may be adhered to the wrapper by hot melt
adhesive (e.g. various polyester adhesives), high m.p. polyethylene
glycol, or emulsion-type adhesive such as PVA.

[0043]The particulate material may be directly or indirectly adhered to
the wrapper. An example of direct adherence is wherein the particulate
material is affixed to the wrapper (such as the inner surface thereof) by
means of a suitable adhesive. An example of indirect adherence is wherein
the particulate material is affixed to an intermediate layer (which may
be made of paper or other suitable support matrix--such as a textile
material--or combinations thereof) by means of a suitable adhesive and
wherein the intermediate layer is affixed to the wrapper (such as the
inner surface thereof) by means of a suitable adhesive.

[0044]Suitably the additional filter section(s) of the filter may be
comprised of conventional fibrous cellulose acetate, polypropylene or
polyethylene material or gathered paper material. The additional filter
section(s) may optionally comprise one or more additives, for instance
disposed upon or within the material of the filter element may be further
flavouring materials, as described above, which are released or eluted
from the filter element during use.

[0045]The cylindrical element of the first section at the mouth end may be
made from a variety of materials, for example, cellulose acetate tow,
cellulose, paper, cotton, polypropylene web, polypropylene tow, polyester
web, polyester tow or combinations thereof. It is preferred that the
element comprises cellulose acetate.

[0046]In addition, the pressure drop and/or mechanical filtration
efficiency of the filter sections can be selected to achieve the desired
smoking mechanics and filtration characteristics as may be required with
the specific product design desired.

[0047]A part of the filter may comprise a catalyst. Advantageously the
catalyst facilitates the conversion of carbon monoxide (CO) to carbon
dioxide (CO2) in the vapour phase of the smoke. It is much by
preference that the catalyst is highly selective for carbon monoxide.
Suitably the catalyst may be one of the group consisting of transition
metal oxides, silica, alumina, zeolites, impregnated carbon, for example,
carbon impregnated with metals.

[0048]Suitably the filter and/or smoking article according to the present
invention may comprise ventilation means. For example, the ventilation
means may comprise one or more holes in the wrapper engaged around the
filtration material of the second section. The holes may advantageously
be positioned in regions of the wrapper to which the particulate material
is not adhered. Ventilation holes are often formed in filter wrappers by
laser piercing. Carbon granules in the region where ventilation is
required can cause the laser to produce sparks when the holes are being
made. Positioning the ventilation holes in gaps between the portions of
particulate material addresses this problem.

[0049]The ventilation means may comprise perforation holes in the tipping
wrapper used to interattach the filter and the rod of wrapped smokable
filler (e.g. tobacco) material.

[0050]Alternatively the ventilation means may be provided by the use of a
porous tipping wrapper used in conjunction with a perforated plugwrap.
The porous tipping wrapper may be porous over its full extent or over
only a localised extent, which extent is in registration with the
underlying perforated plugwrap.

[0051]The ventilation means may further be provided at or close to the end
of the rod of wrapped smokable filler (e.g. tobacco) material. The
ventilation means may be provided in the tipping wrapper or in the
cigarette paper wrapper enwrapping the smokable filler (e.g. tobacco)
material.

[0052]Suitably, the filter may be attached to a wrapped smokable filler
material rod (i.e. a wrapped tobacco rod for instance) by conventional
tipping overwrap to form a smoking article. The tipping overwrap may be
ventilating or non-ventilating overwrap.

[0053]The length of the smoking material rod is advantageously at least 60
mm and the rod should preferably yield not less than six puffs, and more
preferably not less than seven puffs when smoked under standard machine
smoking conditions. The rod is preferably of uniform cross-sectional
shape and dimensions throughout the length of the rod.

[0054]The wrapper enwrapping the smoking article may comprise a burn
additive, such as sodium and/or potassium citrate, for example. Other
suitable burn additives, such as sodium or potassium salts, such as
acetate and tartrate; mono-ammonium phosphate, and di-sodium hydrogen
phosphate, for example, will be known to the skilled man. The burn
additive may be present in the range of 0.5-2.5% by weight of the
wrapper. The wrapper may also have a base weight in the range of 20-40
g/m2.

[0055]The wrapper of the smoking article may alternatively or in addition
be a non-paper wrapper, such as the wrappers described in International
Patent Applications, Publications Nos. WO 96/07336 and WO 01/41590. Such
wrappers assist in the reduction of sidestream smoke components, but
still provide a smoking article which has burning and ashing
characteristics similar to conventional products, i.e. the wrappers allow
the smoking article to burn down and ash in a similar way to conventional
products.

[0056]Suitably, the smokable filler material may be tobacco-containing
material or a tobacco substitute material. Preferably the smokable
material is a tobacco material. Suitably the tobacco material comprises
one or more of stem, lamina, tobacco dust and reconstituted tobacco. It
is preferred that the tobacco material comprises one or more of the
following types: Virginia or flue-cured tobacco, Burley tobacco, Oriental
tobacco, reconstituted tobacco. It is much by preference that the
smokable material comprises a blend of tobacco material. Advantageously
the smokable material comprises 10-80% Virginia tobacco, 10-60% Burley
tobacco, 0-20% Oriental tobacco, 0-120% reconstituted tobacco and 0-30%
expanded tobacco.

[0057]The term `carbon` as used herein can be taken to cover a material
which is substantially solely carbon and any carbon precursors, such as
carbonaceous material. As used herein the term carbonaceous includes
material which has been pyrolysed, which material preferably contains
carbon, although some incomplete combustion products may still be
present. Ready pyrolysed coconut fibre may, for example, be the
carbonaceous material from which carbon is derived.

[0058]As used herein, the term `smoking material` or `smokable filler
material` means any material which can be used in a smoking article. It
does not necessarily mean that the material itself will necessarily
sustain combustion.

[0059]As used herein, the term `smoking article` means any product that is
used in the tobacco industry and includes smokable products or similar
products for delivering an aerosol to the consumer. Smoking articles
include cigarettes, cigars, cigarillos and similar articles.

[0060]In order that the present invention may be clearly understood and
readily carried into effect reference will now be made, by way of
example, to the accompanying drawings in which:

[0061]FIG. 1 shows a longitudinal cross-sectional view of a filter having
a recess at the mouth end according to the prior art;

[0062]FIG. 2 shows a longitudinal cross-sectional view of a filter
according to one embodiment of the present invention;

[0063]FIG. 3 shows an end view from the mouth end of a filter according to
one embodiment of the present invention;

[0064]FIG. 4 shows a longitudinal cross-sectional view of a filter
according to a further embodiment of the present invention; and

[0065]FIG. 5 shows a longitudinal cross-sectional view of a tilter
according to an alternative arrangement of the present invention.

[0066]FIG. 1 shows a known filter 1 attached to a tobacco rod 2 (only a
portion of which is shown) to form a cigarette. Filter 1 consists of a
plug of cellulose acetate 3 (filtration material) circumscribed by a
plugwrap 4. The plugwrap 4 is longer than the plug of cellulose acetate 3
and overhangs the plug of cellulose acetate at the mouth end of the
filter 1 to create a recess having a depth typically of approximately 5
mm. The length of overhang of the plugwrap 4 is designated in FIG. 1 by
the reference character x. The filter 1 is attached to the tobacco rod by
a tipping wrapper 5 in the conventional manner. The plugwrap 4 is
typically a wrapper having a high base weight, for example 100 g/m2
to provide rigidity to the filter 1.

[0067]FIG. 2 shows a filter 1 in accordance with the present invention in
which a first section at the mouth end of the filter 1 comprises a
tubular plug of cellulose acetate 6 having a hollow central core,
designated by reference numeral 7 in FIG. 2. The filter 1 also consists
of a second section at the tobacco rod end of the filter 1 and adjacent
the first section. The second section comprises a plug of cellulose
acetate filtration material 3 circumscribed by a plugwrap 4, which
plugwrap 4 may also circumscribe the cellulose acetate plug 6 of the
first section. Alternatively the plugs 3, 6 may each be circumscribed by
a respective individual plugwrap. The filter 1 is attached to a tobacco
rod 2 to form a cigarette by a standard tipping wrapper 5. The plugwrap 4
and/or the tipping wrapper 5 may be ventilated (not shown) at any point
over their surface and to a varying amount dependent on the particular
product. The plug of cellulose acetate 6 of the first filter section may
for instance be 7 mm in length and provides rigidity to the mouth end of
the filter 1 and allows a conventional plugwrap 4 to be used without
reducing strength.

[0068]FIG. 3 shows the filter of FIG. 2 in end view from the mouth end
thereof. The cylindrical plug of cellulose acetate 6 defines a hollow
core 7 longitudinally along the centre of the plug 6. The plug of
cellulose acetate filtration material 3 of the second section can be seen
at the far end of the hollow core 7. The thickness of the cylindrical
plug of cellulose acetate 6 is defined by the outer surface of the plug 9
and by the inner surface of the plug 8. This thickness, designated by
reference character z in FIG. 3, may vary depending on the desired size
of the recess at the mouth end of the filter 1. The cylindrical plug of
cellulose acetate 6 is circumscribed by a plugwrap (not shown) and is
surrounded by a tipping wrapper (not shown) to join the filter 1 to a
tobacco rod in a formed cigarette. The inner-surface of the plug of the
first filter section may be of any desired shape and thus serve to create
a recognizable shape for the hollow core 7.

[0069]The filter 1 of FIG. 4 comprises all of the features of FIG. 2, and
same reference numerals are used to denote equivalent features, with the
addition of a particulate activated carbon 10 adhered to the inner
surface of the plugwrap 4 circumscribing the plug of cellulose acetate 3
of the second filter section. The carbon 10 extends the entire
longitudinal length of the second section, being for instance 20 mm in
length. The thickness of the wall of the plug of cellulose acetate of the
first filter section is sufficient to cover the carbon at the position of
abutment between the first and second filter sections and prevent any
carbon 10 becoming loose and escaping into the first filter section or
beyond the mouth end of the filter 1.

[0070]FIG. 5 shows a filter 1 which comprises all of the features of FIG.
4, with the alteration in the length of the layer of carbon 10.
Particulate activated carbon 10 extends over only a portion of the
plugwrap 4 which circumscribes the plug of cellulose acetate 3 of the
second filter section. The carbon 10 extends from the end of the plug of
cellulose acetate 3 nearest the mouth end of the filter 1 to a position
part way along the plug 3 towards the tobacco rod 2.

[0071]All publications mentioned in the above specification are herein
incorporated by reference. Also included herein by reference is our
co-pending UK patent application filed on 6 Jul. 2006 and having
application number 0613483. Various modifications and variations of the
described methods and system of the present invention will be apparent to
those skilled in the art without departing from the scope of the present
invention. Although the present invention has been described in
connection with specific preferred embodiments, it should be understood
that the invention as claimed should not be unduly limited to such
specific embodiments. Indeed, various modifications of the described
modes for carrying out the invention which are obvious to those skilled
in the art are intended to be within the scope of the following claims.